This study investigated the associations among age, physical activity level, knee muscle function, and neuromuscular junction (NMJ) biomarkers in a cohort of 80 middle-aged and young men residing in the Republic of Korea. Despite comparable levels of physical activity between the groups, the middle-aged participants exhibited significantly higher body fat percentage, elevated levels of the neurodegeneration marker neurofilament light chain (NfL), and a marked decline in lower-extremity muscle function compared to their younger counterparts. Advancing age was negatively associated with knee extensor peak torque, body weight–normalized torque (BW/PT), and the rate of torque development at 0.18 s (RTD@0.18s). In contrast, higher physical activity levels were positively correlated with certain indicators of muscle function and were associated with lower circulating concentrations of the NMJ degeneration marker, C-terminal agrin fragment (CAF). These findings suggest that neuromuscular decline and muscle function deterioration may begin as early as middle age. The results underscore the importance of implementing tailored exercise regimens and lifestyle interventions to preserve neuromuscular health and prevent early-onset muscle loss.

This exploratory randomized trial evaluated an eight-week combined isometric and elastic-resistance program in community-dwelling women aged 70 years or older. Forty-nine participants were randomized to exercise (EG; n = 24) or control (CG; n = 25). Twenty-two EG participants completed the intervention and follow-up; two had no post-intervention measurements because of scheduling conflicts. All randomized participants were included in the intention-to-treat analysis using 50 data sets generated by predictive mean matching and baseline-adjusted analysis of covariance. Compared with the CG, the EG showed lower body weight (adjusted mean difference [AMD], −0.45 kg), BMI (−0.19 kg/m²), 4 m gait time (−0.96 s), and five-repetition chair-stand time (−1.60 s), and higher skeletal muscle mass (0.38 kg), calf circumference (0.80 cm), and handgrip strength (1.01 kg). The corresponding primary 95% confidence intervals excluded zero, although the skeletal-muscle-mass interval narrowly included zero under conservative imputation. Differences in body fat percentage (−0.33 percentage points; 95% CI, −1.24 to 0.58) and tandem-stance time (0.79 s; 95% CI, −0.42 to 2.00) were inconclusive. These preliminary findings suggest that the program may improve selected body-composition and functional outcomes. Larger prospectively powered trials are required to confirm their magnitude, clinical relevance, and durability.